///bilateral constraint between two dynamic objects
///positive distance = separation, negative distance = penetration
public static void ResolveSingleBilateral(RigidBody body1, ref Vector3 pos1,
RigidBody body2, ref Vector3 pos2,
float distance, ref Vector3 normal, ref float impulse, float timeStep)
{
float normalLenSqr = normal.LengthSquared();
Debug.Assert(System.Math.Abs(normalLenSqr) < 1.1f);
if (normalLenSqr > 1.1f)
{
impulse = 0f;
return;
}
Vector3 rel_pos1 = pos1 - body1.GetCenterOfMassPosition();
Vector3 rel_pos2 = pos2 - body2.GetCenterOfMassPosition();
//this jacobian entry could be re-used for all iterations
Vector3 vel1 = body1.GetVelocityInLocalPoint(ref rel_pos1);
Vector3 vel2 = body2.GetVelocityInLocalPoint(ref rel_pos2);
Vector3 vel = vel1 - vel2;
Matrix m1 = MathUtil.TransposeBasis(body1.GetCenterOfMassTransform());
Matrix m2 = MathUtil.TransposeBasis(body2.GetCenterOfMassTransform());
JacobianEntry jac = new JacobianEntry(m1,m2,rel_pos1,rel_pos2,normal,
body1.GetInvInertiaDiagLocal(),body1.GetInvMass(),
body2.GetInvInertiaDiagLocal(),body2.GetInvMass());
float jacDiagAB = jac.GetDiagonal();
float jacDiagABInv = 1f / jacDiagAB;
float rel_vel = jac.GetRelativeVelocity(
body1.GetLinearVelocity(),Vector3.TransformNormal(body1.GetAngularVelocity(),m1),
body2.GetLinearVelocity(),Vector3.TransformNormal(body2.GetAngularVelocity(),m2));
float a = jacDiagABInv;
rel_vel = Vector3.Dot(normal,vel);
//todo: move this into proper structure
float contactDamping = 0.2f;
if(ONLY_USE_LINEAR_MASS)
{
float massTerm = 1f / (body1.GetInvMass() + body2.GetInvMass());
impulse = - contactDamping * rel_vel * massTerm;
}
else
{
float velocityImpulse = -contactDamping * rel_vel * jacDiagABInv;
impulse = velocityImpulse;
}
}